There is known a method for trenchless laying of pipes in which a pipe is lowered down a vertical shaft and then forced through the ground in a preset direction.
An arrangement for carrying out the method comprises a power unit secured in a shaft chamber for forcing the pipes in the ground, and a device for evacuating the ground (cf., U.S.S.R. Inventor's Certificate 662, 669).
A disadvantage of this method and arrangement is that the length to which the pipe can be forced into the ground is limited. This limitation is accounted for in that the entire force produced by the power unit is imparted to the end of the pipe inside the shaft, whereas the strength and rigidity of the pipe are low, making the pipe susceptible to deformation.
There is also known a method for trenchless laying of pipes in which pipe sections are forced through the ground in a preset direction, the pipe sections being lowered down one of vertical shafts and removed as they are forced through the ground from the second vertical shaft, after which a stationary pipe is layed. Forcing each pipe section is accompanied by removal of earth using screw conveyers and earth working equipment for evacuating the earth. In this method, use is made of pipe sections of a diameter substantially greater than the diameter of stationary pipes layed subsequently, which is necessitated by positioning in such pipe sections of the earth working and conveying equipment.
In addition, such methods require substantial technical facilities, and are very expensive.
An arrangement for carrying out this method comprises a power unit engageable with the rear end of each pipe section as they are forced through the ground, at least one intermediate hydraulic power unit positioned between two adjacent pipe sections and capable of relative movement as they are forced into the ground, and earth working and conveying means. The intermediate hydraulic power unit has the form of a hydraulic power cylinders arranged about the periphery inside the pipe sections (cf., West German Publication 3,122,710).
One disadvantage of the above arrangement resides in that in the confined space for working the ground, the hydraulic power cylinders of the intermediate power unit constrict the useful working space inside the pipe. This construction of the intermediate power unit makes access to the shaft chamber difficult and complicates evacuation of earth from the shaft, resulting in low efficiency of the arrangement. Another disadvantage is that the hydraulic power cylinders are rigidly secured to the adjacent thin-wall pipe sections, whereby substantial forces imparted by the cylinders can deform the pipe sections to result in low reliability of the prior art arrangement.